VIDEO ANIMATION: ethylene molecule C₂H₄

Ethylene (Ethene) molecules have 2 carbon atoms and four hydrogen atoms. It is the first of the alkenes. In ethylene, the two carbon atoms are joined by a double bond (which renders the molecule rather inflexible) and all the atoms lie in the same plane. The C=C-H bond angle is slightly greater than 120⁰ and the H-C-H bond angle is slighly less than 120⁰. In this computer graphic, carbon is shown as black and hydrogen as green.

Ethylene is very important commercially where it forms the basis of many compounds including (its polymer) polyethylene or polythene. It forms ethanol by combination with water: C₂H₄ + H₂O = CH₃CH₂OH (a process called hydration). It can be catalytically combined with hydrogen to form ethane.